Heavy pulp including particles of ferrochrome alloy having a smooth and spherical surface area



HLGABLER ETAL 3,454,498- INCLUDING PARTICLES OF FERROCHROME ALLOY HAVING I A smoom AND SPHERICAL SURFACE AREA July 8, 1969 HEAVY PULP Original Filed Nov. 25, 1964 mm m 1 5 Mn 3 an an m mu of Me 3 3021528 5?. v

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ENTORS ABLER GERHAADT, ANDLER. ATTORNEYS United States Patent Ofice 3,454,498 Patented July 8, 1969 3,454,498 HEAVY PULP INCLUDING PARTICLES OF FERRO- CHROME ALLOY HAVING A SMOOTH AND SPHERICAL SURFACE AREA Hellmut Gable: and Wilfried Gerhardt, Knapsack, near Cologne, and Joachim Kandler, Bruhl, near Cologne, Germany, assignors to Knapsack-Griesheim Aktiengesellschaft, Knapsack, near Cologne, Germany Continuation of application Ser. No. 413,737, Nov. 25, 1964. This application Aug. 22, 1966, Ser. No. 579,468 Claims priority, applicatiolnsglzrmany, Dec. 6, 1963, 5 Int. Cl. C09k 3/00 U.S. Cl. 25260 2 Claims This application is a continuation of application Ser. No. 413,737 filed Nov. 25, 1964, now abandoned.

The present invention'is concerned with a pulverulent ferrochrome alloy consisting of particles having a smooth and spherical surface area, and the ferrochrome alloy consisting essentially of 10 to 30% by weight chromium, 0.05 to 1.0% by weight aluminum, 0.01 to 0.5% by weight carbon, and 0.5 to 5% by weight silicon. The alloy may also contain small proportions of customary accompanying elements, such as phosphorus, sulfur, manganese, and titanium, the balance being iron. The present invention is more especially concerned with ferrochrome alloys consisting essentially of 13.5 to 20% chromium, 0.05 to 0.3% aluminum, 0.03 to 0.1% carbon, and 1.5 to 3.0% silicon, the balance being iron. Pulverulent alloys having such composition and consisting of particles havinga smooth and spherical surface area are very suitable for use e.g. as a heavy material for the float-sink dressing of ores and/or minerals, or as a filler or loading material e.g. for blank fire or training ammunition, as will more fully be described hereinafter. The density of the alloy varies between 7.2 to 7.8 g./cc. The ferrochrome particles substantially have a spherical, drop-like or elongated shape. The pulverulent alloy may consist of atomized ferrochrome prepared in conventional manner by atomizing a corresponding melt. The ferrochrome melt, which may have been prepared by electrothermal means, is atomized with the aid of water, steam, air, nitrogen and the like under a pressure of about 2 to 13 atmospheres (1 to 12 atmospheres gauge pressure) and has a temperature 50 to 500, preferably 100 to 150 centigrade degrees above the respective melting temperature.

Spherical ferrochrome particles can also be prepared in finely divided form from molten material in customary manner by directly transforming the molten material into powder form on a granulating plate or in a granulating groove, the molten material being comminuted and quenched advantageously with water, or with steam, air, nitrogen and the like maintained under a pressure of about 1 to 20 atmospheres (gauge pressure) and forced to issue e.g. through a nozzle.

Ferrochrome particles first obtained in solid form by a conventional grinding can successively be caused likewise in known manner, if desired under pressure and with the aid of an atomizing agent, to travel through a heating zone, e.g. a flame zone, the particles being melted round at least superficially on passing through that Zone and being caused to solidify in a cooling or quenching zone following the heating zone. It is also possible to prepare the spherical-shaped ferrochrome particles by a metal spray process.

The ferrochrome alloy produced in accordance with the present invention should more especially contain:

Percent by wt. Aluminum 0.05-1.0 Carbon 0.01-0.5

or should contain these constituents in the preferred proportional ranges set forth above, because the round and smooth surface area of the ferrochrome particles will disappear outside these ranges and the ferrochrome powder. will increasingly assume a spattered and edged shape having a rough and irregular surface area.

It is already known that finely divided and watersuspended mineral or metal powders can be used for making so-called heavy pulps for use in ore-dressing. It is also known that these mineral or metal powders can be used in the form of particles having a smooth and roundedoif, preferably a spherical shape. As compared with ground powder, these latter particles undergo lesser frictiori and they will produce a pulp of lower viscosity or consistency. The powders consisting of particles having a rounded-01f or a wholly or partially spherical shape also permit suspending a larger proportion of solid matter in the heavy pulp which results in the suspension having a specific density, i.e. a unit weight number, considerably higher than the suspensions produced with ground powders, without'the heavy pulp consistency being increased. The content of solid matter in the heavy pulps is conveniently identified by indicating the proportion of solid matter contained therein in percent by volume. Two possibilities are offered for making a pulp having a given, e.g. an especially high unit weight number without excessive increase of the pulp consistency for application under practice conditions. Firstly, one can use a heavy substance of an especially high density and secondly one can use a heavy substance consisting of particles having a smooth and rounded-off, preferably a spherical surface area, which enable the solid matter content in percent by volume of the pulp to be increased.

A heavy substance for use in ore-dressing has to meet various specifications. It should be substantially corrosion-resistant under the operating conditions and it should be ferro-magnetic in order to permit freeing the heavy pulp from sludge and ore abrasion fines.

The heavy substances used for making the various suspensions substantially include magnetite and ferrosilicon containing about 15% Si. It is known and especially advantageous in accordance with what has been said above to use the ferrosilicon powder in the form of particles having a rounded-off or a wholly or partially spherical shape. It is also known that such ferrosilicon powder can be alloyed with nickel and/ or copper with the silicon content being slightly reduced concurrently therewith; such alloyed material even has a density higher than unalloyed ferrosilicon containing 15 Si. The maximum pulp densities obtainable with ferrosilicon so alloyed are as high as about 4.1 g./cc., corresponding to a solid matter content of about 50% by volume for a density of the solid of 7.2 g./cc.

It is the object of the present invention to atomize a ferrochrome alloy not previously used for the float-sink dressing so as to obtain a powder having a higher density and consisting of particles having a rounded-01f or a partially or wholly spherical shape. Appropriate selection of the chromium content results in the formation of a powder of good corrosion resistant and magnetic properties which can be regenerated as described above. The

Silicon process of the present invention enables the production of metal powders having a density of up to 7.8 g./cc. which permit obtaining a pulp density as high as 4.4 g./cc. for a solid matter content of about 50% by volume.

The chromium content of the powders produced in accordance with the present invention may vary within wide limits. Advantageously, it is adjusted so as to vary within the limits of 5 to 30%, preferably 13.5 to 20%. Lower chromium contents involve lower resistance to corrosion, whereas higher chromium contents involve the formation of metal powders of lower density and thus e.g. the formation of suspensions of lower pulp density.

The ferrochrome powder consisting of particles having a rounded-off and advantageously a spherical shape, prepared in accordance with the present invention, can also be used for applications other than for the float-sink dressing. It can be used, for example, as a filler e.g. in blank fire and training ammunition. The high apparent density obtainable with the powder, which may be as high as about 5.0 to 5.4 g./cc. and which corresponds to the material occupying a given volume to an extent of about 70%, is especially advantageous for such application. Ground powders, e.g. ferochrome powders of identical chromium content, on the other hand occupy less than 60% of a given volume, which means that the material has an apparent density correspondingly lower. The term apparent density as used herein is understood to mean the density which is obtained after intense stamping or vibrating treatment and which, therefore, can also be termed stamp or vibration density.

The ferrochrome alloy produced in accordance with the present invention can be admixed with further metal powders, and especially ferrochrome can be alloyed with further metals, when intended for use as a filler. The metal powders admixed or the components alloyed therewith include e.g. nickel, lead, tungsten, and the like.

The ferrochrome particles are generally employed in the form of grains of which at least a 90% by weight proportion has a size smaller than 0.3 mm. Grains of which an about 50% by weight proportion has a size smaller than 0.06 mm. are especially suitable for use in the floatsin'k dressing, but there may also be used an about 90% by weight proportion consisting of grains smaller than 0.06 mm.

EXAMPLE 1 13 kg. ingot iron containing 0.01% C and 5 kg. ferrochrome containing 60% er and 0.3% C were melted in a tiltable electric furnace while adding 0.7 kg. ferrosilicon containing 75% Si and 0.05 kg. Al. The resulting melt was poured at a temperature of 1,780 C. through a nozzle having a pouring gate 12 mm. wide, and atomized with a vapor jet issuing through an annular slit nozzle arranged concentrically around the pouring jet. The vapor pressure was 4 atmospheres (gauge pressure). The atomized product was quenched with water and dried. A powder consisting of spherical-shaped particles was obtained, of which a 80% proportion could be passed through a screen with meshes 0.25 mm. wide. 90% of the particles obtained had an almost ideal spherical shape. The pycnometer density of the material was found to be 7.6 g./cc. The final product, i.e. the atomized powder was analyzed and found to contain:

Percent by wt.

EXAMPLE 2 A lumpy ferrochrome alloy containing 16.5% by Weight chromium was ground and the apparent density of the resulting ground powder was compared with the density of the atomized ferrochrome alloy of Example 1. Screen analysis 4 Percent: Mm.

Apparent density of ground ferrochrome alloy: 4.60 g./ cc. Apparent density of atomized ferrochrome alloy: 5.25 g./cc.

EXAMPLE 3 A ferrochrome alloy 16% by weight Cr; p=7.6 g./ cc.) atomized in accordance with the present invention and conventional ferrosilicon alloys (15% by weight Si; =6.8 g./ cc.) obtained by atomization and grinding, respectively, were tested for their applicability to the float-sink dressing. The data indicated in the following table for the pulp densities and viscosity, which are also graphically plotted as curves in the accompanying diagram, show that a heavy pulp made with atomized ferrochrome particles enables for the same viscosity at substantially higher pulp density to be obtained than a heavy pulp prepared with ferrosilicon, or enables for the same pulp density the pulp viscosity (consistency) to be reduced.

(1) Ferrosilicon 15% by weight Si, ground, =6.8 g./ cc.

Pulp density (g./cc.): Viscosity, centipoises (2) Ferrosilicon 15 by weight Si, atomized, p=6.8 g./ cc.

Pulp density (g./cc.): Viscosity, centipoises 1. Heavy pulp composition consisting essentially of water and a finely divided, water-suspended metal powder for the float-sink dressing of a substance selected from the group consisting of ores and minerals, said metal powder consisting of particles having a smooth and rounded-oil surface and wherein the said metal powder is a ferrochrome alloy having a density of 7.2 to 7.8 g./cc. and consisting essentially of 10 to 30% by weight chromium, 0.05 to 1.0% by weight aluminum, 0.01 to 0.5% by weight carbon, and 0.5 to 5% by weight silicon, the balance being substantially iron, and the pulp density ranging between 3.37 and 4.4 g./cc.

2. The pulp of claim 1 wherein the ferrochrome alloy consists essentially of 13.5 to 20% by weight chromium, 0.05 to 0.3 percent by weight aluminum, 0.03 to 0.1% by weight carbon, and 1.5 to 3.0% by weight silicon, the balance being substantially iron.

(References on following page) 5 6 References Cited L. DEWAYNE RUTLEDGE, Primaly Examiner.

UNITED STATES PATENTS W. W. STALLA'RD, Assistant Examiner. 2,774,734 12/1956 Rodis et a1. 25260 2,878,518 3/1959 Klee 25260 5 US. Cl. X.R. 3,312,543 4/ 1967 Hofiman et a1. 252-60 75 .5; 209 172'5 FOREIGN PATENTS 63 0,744 6/193 6 Germany. 972,687 9/ 1959 Germany. 703,204 4/ 1931 France. 

1. HEAVY PULP COMPOSITION CONSISTING ESSENTIALLY OF WATER AND A FINELY DIVIDED, WATER-SUSPENDED METAL POWDER FOR THE FLOAT-SINK DRESSING OF A SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF ORES AND MINERALS, SAID METAL POWDER CONSISTING OF PARTICLES HAVING A SMOOTH AND ROUNDED-OFF SURFACE AND WHEREIN THE SAID METAL POWDER IS A FERROCHROME ALLOY HAVING A DENSITY OF 7.2 TO 7.8 G./CC. AND CONSISTING ESSENTIALLY OF 10 TO 30% BY WEIGHT CHROMIUM, 0.0K TO 1.0% BY WEIGHT ALUMINUM, 0.01 TO 0.5% BY WEIGHT CARBON, AND 0.5 TO 5% BY WEIGHT SILICON, THE BALANCE BEING SUBSTANTIALLY IRON, AND THE PULP DENSITY RANGING BETWEEN 3.37 AND 4.4G./CC. 